In known devices of this type, speed variations of several km/h occur in regulated travel. In other words, the vehicle does not move, as desired, at a constant speed but at a speed that varies about an average value. This effect results essentially from the play of the mechanical elements between the setting drive and the throttle valve, which only in a very few vehicles that are provided with a favorable arrangement of the throttle control rod, and at a substantial expense for manufacture and assembly, can be reduced to a tolerable amount. On account of this considerable expense, a certain swinging of the actual speed about an average value in the regulated state has hitherto, even in these vehicles, always been accepted.